It has been known to provide an optical film such as a phase difference film, a polarizing film, and a brightness enhancing film to a display device such as a liquid crystal display device. Such an optical film is produced collectively in a certain amount into a long-length shape from the viewpoint of production efficiency, and the long-length film is stored as a wound bode. After storage for a fixed period, the long-length film is unrolled from the wound body. If necessary, the long-length film is bonded to another long-length film by a roll-to-roll method or the like, and later subjected to shaping such as punching. The long-length film is then incorporated into a liquid crystal display device or the like, and used.
A technique of bonding a protective film to a long-length optical film has been known for improvement of protection and handling properties of the optical film during winding of the long-length optical film (see Patent Literature 1). The protective film is bonded to the optical film to form a multilayer film, and the multilayer film is wound to form a wound body, with which an advantageous effect can be obtained. For example, the handleability during winding and unrolling can be improved, damage caused by sticking of the optical film to another optical film can be prevented, and the optical film can be protected against dust and the like. The protective film used in such applications is often prepared as a long-length film before bonding to the optical film for convenience of operation. Such a long-length film is usually wound and stored as a wound body, and unrolled from the wound body before bonding to the optical film, and then used.